Ideal Gas Equation And Gas Laws
A sealed rigid container holds an ideal gas whose absolute temperature is doubled while its volume is kept fixed, so what happens to the pressure exerted on the walls?
Select the correct option:
Solution
The pressure becomes twice its original value
The behaviour here is governed by the ideal gas equation from NCERT Class 11, Chapter 13 (Kinetic Theory), namely PV=nRT, which links pressure, volume and absolute temperature for a fixed amount of gas. Since the container is rigid and sealed, both the volume V and the number of moles n stay constant, so pressure is directly proportional to absolute temperature, giving the Gay-Lussac relation P∝T. Writing T1P1=T2P2 and substituting T2=2T1 yields P2=2P1, so the pressure exactly doubles. The option claiming pressure halves reverses the proportionality and would apply if temperature were halved. The option that pressure is unchanged ignores that heating increases molecular collision frequency and momentum transfer to the walls. The option that pressure quadruples wrongly assumes P∝T2, which no gas law supports. A quick plausibility check confirms the answer: temperature is measured in kelvin, doubling a positive absolute temperature gives a positive doubled pressure, consistent in both sign and magnitude with a heated rigid vessel.
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About This Question
- Subject
- physics
- Chapter
- kinetic theory of gases
- Topic
- ideal gas equation and gas laws
- Difficulty
- Easy
- Year
- 2025
Solution
Correct Answer:
The pressure becomes twice its original value
The behaviour here is governed by the ideal gas equation from NCERT Class 11, Chapter 13 (Kinetic Theory), namely PV=nRT, which links pressure, volume and absolute temperature for a fixed amount of gas. Since the container is rigid and sealed, both the volume V and the number of moles n stay constant, so pressure is directly proportional to absolute temperature, giving the Gay-Lussac relation P∝T. Writing T1P1=T2P2 and substituting T2=2T1 yields P2=2P1, so the pressure exactly doubles. The option claiming pressure halves reverses the proportionality and would apply if temperature were halved. The option that pressure is unchanged ignores that heating increases molecular collision frequency and momentum transfer to the walls. The option that pressure quadruples wrongly assumes P∝T2, which no gas law supports. A quick plausibility check confirms the answer: temperature is measured in kelvin, doubling a positive absolute temperature gives a positive doubled pressure, consistent in both sign and magnitude with a heated rigid vessel.
This easy difficulty physics question is from the chapter kinetic theory of gases, covering the topic of ideal gas equation and gas laws. It appeared in the 2025 exam.
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